1. Technical Field
The present invention relates to ferroic materials, and more particularly to circuit elements comprising ferroic materials.
2. Background
Electronic devices are often fabricated by assembling and connecting various components (e.g., integrated circuits, passive components, chips, and the like, hereinafter “chips”). Many components, particularly semiconductors, are sensitive to spurious electrical events that apply excessive voltage to the devices in what is termed an overvoltage condition. Examples of sources of overvoltage conditions include electrostatic discharge (ESD), back electromotive force (EMF), lightning, solar wind, switched electromagnetic induction loads such as electric motors and electromagnets, switched heavy resistive loads, large current changes, electromagnetic pulses, and the like. Overvoltage conditions may result in a high voltage at a device containing active and/or passive electronic components or circuit elements, such as a semiconductor IC chip, which may cause large current flow through or within the components. The large current flow may effectively destroy or otherwise negatively impact the functionality of such active or passive components or circuit elements.
Some chips include “on-chip” protection against some overvoltage events (e.g., a mild ESD event) that may be expected during packaging of the chip or operation of the respective electronic device (e.g., protection against Human Body Model events).
A chip may be packaged (e.g., attached to a substrate). A packaged chip may be connected to additional (e.g., ex-chip) overvoltage protection devices, that protect the packaged chip against more severe (e.g., higher voltage) overvoltage events. Inasmuch as the on-chip and off-chip overvoltage protection devices are in electrical communication, the off-chip overvoltage protection device may be required to “protect” the on-chip overvoltage protection device. Off-chip overvoltage protection devices using discrete components are difficult to add during manufacture of the substrate. Moreover, on-chip protection is difficult to optimize across a complete system or subsystem. Examples of specifications for ESD testing include IEC 61000-4-2 and JESD22-A114E.
A printed circuit board, printed wiring board, or similar substrate (hereinafter also referred to as PCB) may be used to assemble, support, and connect electronic components. A PCB typically includes a substrate of dielectric material and one or more conductive leads to provide electrical conductivity among various attached components, chips, and the like. Typically, a pattern of metallic leads is plated (e.g., using printing technology such as silk-screening) onto the dielectric substrate to provide electrical connectivity. Alternatively a metallic layer (e.g., a layer of Cu, Ag, Au) is applied to the substrate and subsequently portions of the metallic layer are removed (e.g., etched) resulting in the desired pattern. Multiple layers of conductive patterns and/or dielectric materials may be disposed on a PCB. The layers may be connected using vias. Printed circuit boards including 14 or more layers are not uncommon.
A PCB is typically used for supporting and connecting various integrated electronic components, such as chips, packages, and other integrated devices. The PCB may also support and connect discrete components, such as resistors, capacitors, inductors, and the like, and provide connections between integrated and discrete components. The conductive patterns and/or layers in the PCB and other components or areas within electronic devices sometimes provide paths for conducting overvoltage events that could damage or otherwise negatively impact components.
Discrete components are sometimes manufactured by incorporating certain functional structures inside a supporting medium or package. For example, a discrete inductor component may be manufactured by embedding a conductive coil structure inside a ferroic material medium, which may then be further packaged to produce a discrete packaged ferroic inductor component. The discrete ferroic inductor components known in the prior art may be attached to a PCB board to act as an inductor in an electronic circuit. In general, a discrete component that is constructed by embedding a conductive structure in a ferroic material may be referred to as a “discrete ferroic component.” Examples of discrete ferroic components that exist in the prior art include, discrete ferroic inductors and discrete ferroic capacitors. Examples of ferroic materials used in prior art discrete components include ferrites, such as Fe2O3.
FIG. 1A shows a block diagram of a discrete ferroic inductor 100 in the prior art, as described in a document from Shenzhen Sunlord Electronics Co. (Shenzhen), dated Feb. 10, 2007, available from Shenzhen's website, and also available in the file history of this patent (the “Shenzhen Presentation”), which is incorporated by reference herein in its entirety. The inductor 100 of FIG. 1A, is a conductive structure 102 made out of silver (Ag) which is embedded in a ferroic medium. The discrete ferroic inductor 100 of FIG. 1A acts as a discrete ferrite bead. Discrete ferrite beads have been used in the prior art to act as passive low-pass filters by filtering out higher frequency noise. FIG. 1B shows an X-Ray view of a conductive structure 112 represented by the block diagram conductive structure 102 of the discrete ferroic inductor 100 of FIG. 1A, as illustrated in the Shenzhen Presentation.
FIG. 1C and FIG. 1D illustrate a manufacturing process for a discrete ferroic inductor in accordance with the Shenzhen Presentation. In FIG. 1C, a discrete ferroic inductor is manufactured through tape casting, screen printing and then lamination. In FIG. 1D, a discrete ferroic inductor is processed and eventually packaged into a discrete component that could be utilized in an electrical circuit (e.g., by being surface mounted to a PCB).
FIG. 1E illustrates a plot of a transfer curve for a prior art ferrite bead inductor having a structure such as the inductor 100 illustrated in FIGS. 1A and 1B. The plot of FIG. 1E illustrates an example of the impedance characteristic for two different ferrite bead inductors 100. The impedance characteristics vary depending on the material and structure. The signal waveform and noise suppression effect vary depending on the impedance.